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Unusual RT Pro Issue. . .Now confirmed as micromag 2k9 problem!

So I have an RT Pro valve in my micromag and it has an odd issue. I posted up in the level 10 thread but I was told it is not an issue with the bolt so I thought it needs its own thread.

I've got an rt pro valve with a level 10 bolt. I initially had the original reg piston and it worked fine so long as I didn't want to shoot above 260, that is when it started leaking. So I ordered a new reg piston from tunaman. I'm using the .5 carrier. I started off with the red bolt spring. I followed all the guides and turned the velocity up until it first cycles, this happens at about 250fps. Since that is 20fps below where I want to be I thought I'd be good. Well when I try to turn up the velocity to get to field velocity, it doesn't increase at all. I can turn it in until the velocity nut bottoms out and it won't go above 250. I tried all three bolt springs and it is the same case with each one, though at different velocities. Am I missing something crucial here? I am stumped.

Someone suggested to use washers to shim the spring but this had no effect. There are about 3 full turns from when the gun starts cycling at about 250 to when the nut bottoms out. Throughout this range the velocity doesn't change. It stays at 250.

Do you have both springs (inner and outer) in between the reg piston and adjustment nut? If so, consider replacing them.

Also, compare your reg pin assy with the pic at airgun.com. Are all the pieces there? Does it look like the end that is toward the rear of the marker when assembled has been tampered with (e.g. ground/filed)?

2. Did you rebuild the reg pin assembly or the entire valve? What all did you replace?

3. Diassemble the back half of the valve. Check for debris (o-ring segment, dirt, metal shavings, etc.) in front of the reg piston.

4. If #3 checks out, I am still thinking it's the springs. If this thing sat stored for 10 years with the adjustment nut bottomed out, the springs may have relaxed in the compressed state. Or maybe someone put incorrect springs in it to begin with. I'd try new springs.

However, I know it can be frustrating to buy new parts without a guarantee they will work. Does anyone near you have a properly functioning valve you could swap back halves for test? This could help you isolate the problem.

Afterthought #1. You stated you get different velocities with the different bolt springs. Please list starting velocity for each spring. I want to make sure my hypothesis is in line with the data.

Afterthought #2: Do the same debris check as #3 in the pocket that the reg pin assembly sits in. This should cause a leak if there was something in there, except maybe an o-ring, but it's another thing to check. Take a good picture of your reg pin assembly, so we can have a look.

I'm following this on MCB as well. I'm not sure if you have the marker with you or not. You stated there is no debris in the reg piston pocket -- good. My next question is does the reg piston slide freely (as freely as a lubricated o-ring should) in the pocket? Also, does the piston travel all the way to the bottom of the pocket, or does it stop short? If you take the regulator valve pin o-ring out (the one that sits in the face of the rear half of the valve), can you see the brass colored reg piston sitting close to the pocket that the aforementioned o-ring sits in? If not, is the reg piston out of round, nicked, gouged, or otherwise damaged? What about the pocket? Is it out of round, nicked, gouged, or otherwise damaged? Do you see anything that would prevent the reg piston from sliding to the bottom?

Other than the reg springs being severely relaxed, my other hypothesis is that the reg piston is jammed up, and when you try to increase velocity, all you are doing is pressing the springs against a jammed reg piston. It's not getting to the reg pin like it should.

A quick way to test this is open the two halves of the valve. Remove the large reg body o-ring (the one on the threads that connect the two valve halves). Screw the valve back together. On the last turn assembling the valve, you should feel some resistance. That's the reg pin hitting the reg piston and compressing the springs. You can feel what it's like when they do not hit by removing the reg pin assembly and screwing the halves back together. If you don't feel the resistance, the regulator can't do what it's supposed to. The reason you take the large o-ring out is so that you don't feel the resistance from that when putting the two halves together. Make sure the reg pin assembly is seated all the way before doing this test. Otherwise, you'll feel a "false positive" when screwing the halves together, because you'll feel the resistance of seating the reg pin assembly.

Even if this is correct, the springs might still need to be replaced. However, if you get the piston to slide freely/bottom out, the suggestion of adding a washer behind the springs should make a difference.

sniper42: I checked to make sure the piston was engaging and I can feel it engage on the reg pin. I checked again for any debris in the valve and I'll get chrono readings tomorrow. I also borrowed my buddy's valve that I can swap springs from to see if that is the problem.

sniper42: Ok I switched the halves for my buddy's valve. Velocity started out at 250. I could turn it up to 260 before the piston leaked. I swapped it for my new piston. I could then get the velocity up to about 270 but then within ten shots I ran out of air. So I need to make a trip to the proshop to get more before I can do any more troubleshooting.

sniper42: Yes my tanks were full and above 1500 psi for all testing.

I started switching the back halves. He is running a level 10 but the valve is relatively new to him so it needs to be tuned still, it had a small leak from the bolt so he needs a smaller carrier. I don't know if the fact the I am running an SHP would make a difference in how his level 10 is setup on his gun. Like if he runs his with a standard tank but then puts an shp on it, the bolt would need to be tuned again correct?

sniper42: I don't know if the fact the I am running an SHP would make a difference in how his level 10 is setup on his gun. Like if he runs his with a standard tank but then puts an shp on it, the bolt would need to be tuned again correct?

athomas: No, the level 10 tuning is always dependent on the size match between the bolt stem and the oring. A properly tuned level 10 bolt should work through all chamber pressures, which are unaffected by the input pressure from the tank regulator.

Alas, I have not yet resolved this. Finals week is approaching for me so I won't be able to work on it until they are over and I'm on break. Rest assured I will be back here for help once finals are over.

Just another idea before I forget, and I'm outside my personal experience with this one. Others will need to chime in.

I've focused this whole time on the valve, reading past the original post that you have this in a Micromag. I know very little about Micromags, but didn't some have an improper distance from where the bolt springs seats to the rear frame/field strip screw? If this distance is too short, will it compress the bolt spring excessively, causing sub-par velocities throughout the entire reg adjustment?

If your buddy's rig is fully functional and set to a desired velocity, just switch valves (including bolt and spring). See if his valve cannot obtain a desired velocity in your Micromag body and if your valve can achieve a desired velocity in his body.

Interesting, I hadn't thought of that. I checked the micromag as well as my classic mag. The micromag body is actually .150" longer than the classic mag. And that is with the steel bushing in the micro. Would the body hole being too long cause this sort of problem? I have yet to get air, been busy with work and machining some parts for a buddy's gun. When I do get air I will put the rt valve in my classic body and put the perfectly functioning classic valve in the micro and see if anything changes.

Just another idea before I forget, and I'm outside my personal experience with this one. Others will need to chime in.

I've focused this whole time on the valve, reading past the original post that you have this in a Micromag. I know very little about Micromags, but didn't some have an improper distance from where the bolt springs seats to the rear frame/field strip screw? If this distance is too short, will it compress the bolt spring excessively, causing sub-par velocities throughout the entire reg adjustment?

If your buddy's rig is fully functional and set to a desired velocity, just switch valves (including bolt and spring). See if his valve cannot obtain a desired velocity in your Micromag body and if your valve can achieve a desired velocity in his body.

-Nathan

You know what, I think you hit the nail on the head. I got air today to do some testing. I took my classic mag with functioning classic valve. It was shooting 280fps in the classic body. I changed nothing and put it in the micromag body and it dropped all the way down to 180fps. I tried my rt valve again in the micromag body. Wouldn't go above 250 fps. Changed nothing but put it in the classic body. It then shot beautifully all the way up to 300fps. So the fact that the hole is bored 0.150" longer on the micromag must be causing this issue. This should be a very simple fix now. I am off to turn a new steel bushing for the micromag that is just a little thicker to take up the extra space. I will report back with how a new bushing works.

Well that did the opposite of what I though it would. A thicker bushing, therefore increasing spring pressure, decreased the velocity. I took out the bushing all together and I had no problem getting it to 290 with a clipped spring I had in my toolkit. However being an aluminum body, I imagine it will peen over, over time. I am baffled because the valve works fine in the classic body.

I was expecting a shorter length on the Micromag body, not longer. F=kx, so adding a thicker shim (i.e. compressing the spring more), will put more force against the forward motion of the bolt, reducing velocity.

I'm running out of ideas, especially since the valve seems OK, and I have zilch for experience with Micromag bodies.

It sounds like you have access to machining and inspection equipment. Perhaps you could blue dykem the inside of the Micromag body to see if there is excessive rubbing/binding preventing the bolt from completing its stroke and/or releasing the air properly.

My body has similar measurements. Basically the body hole is bored .150" farther than my classic mag body. So far, that is the only difference I have found. Now with my limited understanding of automags, if the body hole is bored farther, that would put less pressure on the spring equating to higher velocities. However, the exact opposite is happening. Does anyone know what the depth of the hole for the body is supposed to be?

Did a little more digging. Don't have the best news, as some people haven't figured there's out either. The solutions seem to be:

1. Remove detents to see if marker fires better. If so, I don't know where to go from there. Possibly add orings to move the detents out.

2. Remove breech to see if marker fires better. If so, possibly open up the bore of the breech some. More on this later.

3. Try an E-Mag pin (.712"). I read one post where an E-Mag valve worked in the MM2K9 body, but an X-Valve (.750" pin) did not. If it still doesn't work at .712, and you don't want to use it for anything else, you could continue to grind it down until it no longer seals the on/off when you pull the trigger in hopes of finding a magic length. One poster suggested asking PTP what length pin they recommend, but with the varying dimensions/results with these particular bodies, I don't know if that would help.

4. Did you try the dykem idea? If not, one poster said to blue up the ID, and install a Level 7. The Level 7 wouldn't vent when it hits something, so it would be more obvious where it's hitting. But if you're in the mid 200 fps range already, it's probably happening near the end of the bolt stroke, so you wouldn't hear the Level 10 venting.

5. If you have access to a Z-Cal and surface plate, CMM, Faro Arm, etc., you could check the true position between various circles in all the different bores. Back, breech, front. Not really familiar with these, so bear with me. In the end, you're looking for cylindricity, but that can be hard to measure without proper equipment. Knowing diameters along the length of the bore and true positions between those diameters will get you close. If you find something you think you could fix with the equipment you used before, without turning it into a hotdog (valve) in a hallway (body) situation, you might want to try. This was what I eluded to in #2.

Again, I don't know what all you have access to. It's really hard to come to a logical decision without data; the lack of data primarily driven by the seemingly wide tolerances/issues with these bodies. That said, I'm just throwing darts, or re-throwing darts others suggested.